Final answer:
Earth is an oblate spheroid with a roundness ratio of 0.996, indicating it is nearly round but slightly bulged at the equator. Its relatively smooth surface is exemplified by the scaled representation of Mt. Everest at just 0.3 cm on a 30 cm diameter globe.
Step-by-step explanation:
The roundness and smoothness of Earth can be described by comparing its polar and equatorial diameters. Earth has a polar diameter of 12,714 km and an equatorial diameter of 12,756 km, which implies that it is not a perfect sphere but rather an oblate spheroid, bulging at the equator due to its rotation. The roundness ratio given indicates how closely Earth approximates a perfect sphere; the closer the value is to 1, the more spherical it is. With Earth's roundness ratio being 0.996, it is very nearly round, but with a slight equatorial bulge.
The surface of Earth is relatively smooth, with the highest point above sea level being Mt. Everest at about 8.848 km, which is minuscule compared to the diameter of Earth. When scaled down to a globe with a diameter of approximately 30 cm, the height of Mt. Everest would be represented by merely 0.3 cm in a diagram, illustrating the smoothness of Earth's surface on a large scale.